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concertina226 (2447056) writes "Scientists studying the human remains of plague victims found during excavations for London's new Crossrail train line have concluded that humans spread the Black Death rather than rats, a fact that could rewrite history books. University of Keele scientists, working together with Crossrail's lead archaeologist Jay Carver and osteologists from the Museum of London, analyzed the bones and teeth of 25 skeletons dug up by Crossrail. They found DNA of Yersinia pestis, which is responsible for the Black Death, on the teeth of some of the victims."

I am absolutely not going to RTFA or google this, but but aren't bubonic plague and pneumonic plague caused by the same bacteria, Y. pestis? I sat in an armchair about 30 years back and figured out that fleas could never vector out the fatality rate that history indicates. Even if most folks were living like rats at the time. BTW the survival rate is far lower for the pneumonic variety.

Once again, people who don't get their fact straight are confusing the issue.
The Plague (Yersenia Pestis) is spread by fleas on rats. This is a well known and scientific fact. However, it can also be spread by airbourne particle if the infection moves from the lymph nodes (bubos or swollen lumps in the arm pits and groin is where the name bubonic plague comes from) to the lungs.
Pneumonic Plague (Yersenia Pestis in the lung) is extremely contagious and universally fatal. The last I looked, there are no k

Scientists discovered this at least 6 years ago when I watched a documentary about it, and most likely quite a bit before that.

I also recall reading about this years ago. Iceland was mentioned as a solid case of anti-rat evidence. Rats did not live there (and mostly still don't) but the Black Death still wiped out much of the population of Reykjavik.

At the risk of sounding pretentious, that page doesn't list anything I haven't already known for years - in fact, anyone interested in the Black Death should be already aware of all these things.

We've known that some casualties were not bubonic but pneumonic cases, as well as that some were septicemic instead - even the contemporaries were aware of the three distinct forms of the disease, as manifested by their different symptoms, even if they misunderstood its bacterial underpinnings. We've also known that besides primary pneumonic plague (acquired through inhalation), there's secondary pneumonic plague that happens whenever Yersinia pestis spreads into a bubonic or septicemic plague victim's lungs through the bloodstream.

Claiming that we found out that "Rats Didn't Spread Black Death, Humans Did" feels like disingenous piece of reporting, though, because one of the hallmarks of pneumonic plague is its much more rapid onset and considerable lethality (about half the time it takes for bubonic plague to kill you, or something like that?). Within a town, it's entirely possible that the spread of pneumonic plague overtook bubonic plague whenever it got established, but the "spread" of Black Death was global, and the typical progress of pneumonic plague put it at a serious disadvantage when it came to long-distance travel (especially on ships). So chances are that in many, if not most places removed from other places (towns, regions, countries, continents), the primary pneumonic cases were "jumpstarted" by a case secondary pneumonic plague infection resulting from an infected flea bite. (At least, that's how I interpreted the smart books.)

At the risk of seeming pretentious, the entire article is a crock. Y. pestis is a bacterium, not a virus. As has been mentioned, this is a well known hypothesis and the new information might expand that, but there is not way to determine that from TFA.

Note to editors: The International Business Times is a poor source for scientific news.

The International Business Times is a poor source for scientific news.

No kidding. There's no citation or link to a research paper, or mention of a conference where the researchers presented their findings. Not even a link to a university press release (not that that would count for much; those are often written by PR people who don't have a clue what they're talking about). All they have is "The scientists' work will be featured in the documentary Secret History: The Return of the Black Death". What it looks like is that the documentary makers explain how the archaeologists'

Not only were such facts known to researchers, but most SF fans had a pretty good idea by reading the Doomsday Book by Connie Willis. It might be fiction, but it does get quite a few facts right, and overall is a great read.

Influenza faces the same problem as the "overwhelmingly pneumonic plague" hypothesis: too many buboes in the contemporary descriptions for this hypothesis to make sense. As far as I'm aware, buboes either don't develop in pneumonic plague cases at all, or they only develop in those people who live long enough to give the plague bacteria the time necessary to spread into lymph nodes, which must be a tiny minority in primary pneumonic cases. Or does influenza often actually cause swollen, reddish or blackened

Pneumonic plague being transmitted by air isn't news. It's a form of the disease that gets into your lungs, after all. Also, the primary vector isn't rats at all, but fleas, which often go directly from person to person.

The article's credibility is not helped at all when it mentions the plague virus, when it is actually caused by a bacterium.

Except for the reporting screw-up about virus vs. bacteria, this is all just quibbling. The reporters got it wrong as usual, but that doesn't mean that the researchers got it wrong.

Zoonotic diseases (ones that spills over from one animal population to another) always have fantastically complex life cycles. In epidemics of zoonotic diseases it's common for epizootic transmission (transmission between species) to be overtaken by enzootic transmission (transmission *within* a species). For example influenza is a bird pathogen that can cross over into mammalian species like swine and humans. If flu epidemics didn't shift gears from epizootic transmission (bird to human) to enzootic (human to human), they wouldn't be as big a deal. Just stay away from chickens.

So the idea that the black plague was primarily spread among humans enzootically is hardy groundbreaking epidemiology. It certainly doesn't mean that it's not dangerous to live in a place infested with plague-ridden rats. But the shift to enzootic transmission is something that's a bit different from the mosquito or tick borne diseases or occasional, isolated epizootic plague infections we're largely familiar with today.

It's a neat finding, in that it wasn't necessarily expected, but it makes sense in retrospect. In something like West Nile Virus, the natural focus of the pathogen is migratory bird populations that fly thousands of miles. But while a rat can hop on a ship and travel thousands of miles, the vast majority of rats spend their entire lives in a radius of a few hundred feet. Humans are much more mobile than rats; even if a few rats hitch a ride on a ship, they never go anywhere far *without* humans.

What's simplistic is the assumption there has to be only *one* factor involved in a zoonotic epidemic. Without epizootic transmission the plague would not have happened in the first place. That's not news. Without human-to-human enzootic transmission it would not have spread so widely or kill such a high percentage of the population. That is news (I guess -- I didn't work with people doing plauge so I have no direct knowledge of what people in that field thought). Of course before it becomes established science it's going to have to stand up to criticism for a few years.

Doesn't it kind of muddle things that people dislike rats so much they won't admit bubonic plague disappeared along with brown (Norway) rats replacing the black rats that transmitted the disease?

You're being close-minded here. They transported the fleas that was one vector for transmitting the disease.

And what's with "won't admit"? Who's denying? Or do you mean they won't admit that that is enough evidence for a cause and effect conclusion? No, they won't admit that, because that would be rather unscientific.

How about other factors like improvements in sanitation and transportation?

Who gives a rats ass how you feel about rats. It doesn't do anything to illuminate history.

Well, it's rather a simple chain to follow. Black rats were associated with the plague. Brown rats replaced them, plague stopped. Still, the common wisdom still seems to remain "rats" were responsible for spreading the disease, sanitation measures, that apparently arrived after the disease was already gone, getting the credit. Even "transportation improvements", apparently, although those would tend to spread it more.

Well, the Norway (aka "brown") rats are carriers of an almost incredible variety of infectious agents that are human pathogens, including hantavirus and Toxoplasma.

The issue with rats isn't that they're *particularly* susceptible to zoonotic pathogens. The issue is that they're well adapted to living around human habitations,which provide them with excellent protection from predation. With plenty food and shelter and no predators, they reach unnaturally high population concentrations. These populations are "preyed upon" by germs instead of carnivores, because inevitably everything in nature is food for something else. Some of those pathogens will also effect humans, and since those dense colonies are living in close proximity to dense colonies of *humans*, brown rats present a public health concern, even though none of their pathogens have quite the marquee name recognition of The Black Death.

Another example of this phenomenon is the raccoon. Because raccoons are still frequently encountered in natural settings people don't have the same revulsion towards them as they do towards rats, but raccoons are just as well adapted to living with humans as rats are. In places where high raccoon populations live in close proximity to humans, they're a serious health concern. I've known natural science geeks -- people who have no qualms about handing dead animals or picking through animal scat -- to treat suburban raccoons with revulsion. A suburban raccoon can be a terrifying bag of disease, and there are documented cases of people dying as a result of handling their poop.

It doesn't mean racoons are *bad*, or that rats are *bad*. It means that wild animal populations with nearly unlimited resources and no predation are an all-you-can-eat banquet for germs.

add to that in the typical medieval house and even castle it was very difficult to keep the rats out of the human food supply and tracking their dirty little feet and germs everywhere. That's why cupboards and barrels and pot and other stuff were invented to keep the critters out. all those critters crawling all over had to be spreading germs even when people thought their house was "clean".

Interesting arguments. And not all hollow, though I would have used typhus as an example. Just because an animal can be infected by a disease doesn't always mean it is a credible source for transmission to humans. Or that they serve as a reservoir for other animals to catch it. Perhaps Norway rats "can" carry hantaviruses, but the CDC page is quite specific about the rodents that pose a threat to humans carrying it; deer mice one strain, white footed mice another, a third wild "rice rats" and "cotton rats"

The issue is that [rats are] well adapted to living around human habitations,which provide them with excellent protection from predation.

So, don't reflexively kill all the cats, then?

By mid July of 1665 over 1,000 deaths per week were reported in the city. It was rumored that dogs and cats spread the disease, so the Lord Mayor ordered all the dogs and cats destroyed. Author Daniel Defoe (1660 – 24 April 1731) in his Journal of the Plague Years estimated that 40,000 dogs and 200,000 cats were killed.

Your two posts were fascinating, thanks. It has never crossed my mind to think about rats that much, but the sentence about humans effectively keeping them safe from other predators is one of those obvious-in-hindsight things that I probably never would have realised.

As an Australian that has recently relocated to the US, you have also inculcated a new fear of raccoons, which I will now go at lengths to avoid!

Where's the link between the two? How do you prove a cause and effect? Other things also happened at the same time. I'm not saying that this couldn't be the case, but I am saying that we need some evidence before concluding that this is the cause. Circumstantial evidence can be correct, but it can also be wrong.

Where's the link between Norway rats and the plague at all? Domesticated rat pictures published along with stories about the disease? Circumstantial evidence is also quite weak when totally absent. It might be considered "circumstantial" that Norway rats appeared along with the disappearance of the known disease-transmitting ones, in the same niche, but it is fairly well established.

Well, I'm not sure what "people" you are talking about, but if you're talking about "researchers", the answer would be "no". Researchers are definitely not representative of general population of what they "like" and "dislike".

Two war stories follow.

Some researchers in a tropical medicine discovered that a mens room at the school had been infested with tiny little flies. Did they complain to the management? No. They trapped some of the flies, brought them back to the lab and bred them as pets.

I was walking in the woods one day with a zoologist friend of mine, when we came upon a rotting coyote head in the middle of the trail. "Ooh!" she says, "I want to show that to my students!" Whereupon she picks up the head, maggot-ridden eyeholes and all, and pops it into the pocket of her windbreaker.

How big was the dry-cleaning bill?

Calls to mind the story of the young Darwin, who was faced with containing three beetles when he had only two hands. He put the third one in his mouth.

So the idea that the black plague was primarily spread among humans enzootically is hardy groundbreaking epidemiology. It certainly doesn't mean that it's not dangerous to live in a place infested with plague-ridden rats. But the shift to enzootic transmission is something that's a bit different from the mosquito or tick borne diseases or occasional, isolated epizootic plague infections we're largely familiar with today.

What I don't quite get is, if the plague was spread from human to human, how anyone surv

Well, for one thing the fatality rate is less than 100%. And the infection rates were less than 100% too. Were the infection and fatality rates 100%, the epidemic would quickly burn itself out. You can set up a differential equation describing this situation: the rate of transmission is proportional to the chance of transmission and how frequently an infected person encounters an uninfected person. But that frequency of contact drops as populations are decimated, so that a particularly aggressive stra

The word quarantine comes from the italian "quaranta giorni" (40 days) which was a requirement that ships wishing to land at Venice stand isolated offshore for forty days. The policy was enacted to try to stop the spread of a new disease (from the Orient) that had shown up in Venice. It was too late by that time, and the disease went on to kill a third of the population of Europe and became known as the black death.

Beyond that, particularly virulent disease are often self-quarantining. They kill off ever

It's a neat finding, in that it wasn't necessarily expected, but it makes sense in retrospect.

Is everybody insane? Just read Albert Camus, "La Peste" (written in 1947). It describes in detail how the development from bubonic plague to pneumonic plague creates the human-human transmission path with a quite higher lethality rate and spread.

While Camus takes care to get the medical stuff correct, the focus is on the psychology. He certainly was not going to propose any groundbreaking new medical theories. He just works carefully with what was known at the time.

As a species yes, but much like rats - individuals not so much during the era of the Black Death.

Without human-to-human enzootic transmission it would not have spread so widely or kill such a high percentage of the population.

That's a stretch not clearly supported by the available evidence. That the pneumonic form that's spread human-to-human contributed has long been known, but the widest spread and most deaths came from the the rat borne bubonic form.

Well, whole the point of the article is that the pneumonic transmission may have been responsible for more fatalities in the Black Death than previously thought. In any case, it's the same infectious agent, different tissues infected. So Y. pestis can be vectored as bubonic plague and then subsequently spread as pneumonic plague -- or vice versa. That's my understanding, although as I said elsewhere I've never worked on plauge projects so I may be wrong. But it doesn't seem like much of a stretch given po

Wikipedia has a good article on pneumonic plague, I'm sure that not "all" the victims were of the pneumonic form as the disease often starts in a population in the bubonic form frequently spread by fleas [wikipedia.org] which can progress into the more contagious and more virulent pneumonic form; so while rats and rat fleas don't get the sole blame, they still get their share.

I'd always heard rats carried fleas, not that they were the primary vector, and this is something I've carried around in my head for decades. So, even when quarantined, it was still a nasty situation of not really being able to completely contain the spread.

The plague can take 3 forms, at least one of which, pneumonic, infects the lungs and spreads through the air, much like the common cold does. Just because humans had a role in helping to spread it doesn't leave the rats and their fleas off the hook. It is still quite likely that there were multiple vectors combined that caused the rapid spread of the disease.

It could even be more simple than that; I don't remember 100% about the plague era history, but if I remember correctly near end symptoms were vomiting and swelling / cracking of the tongue. In both cases there is high probability that bacterium from the bloodstream would come in contact with the persons teeth. If you really want to get down to it, many victims were buried in mass graves and it is possible that there was cross contamination due to higher level corpses buboes rupturing when they had been to

What a terribly written article. What did the later deaths in the early 1900s have to do with the medieval plague? Did they find DNA on the victims from the 1900s or from the actual plague outbreak? What does DNA on the teeth have to do with and what does it indicate? Totally worthless crap article, through and through.

You have to re-read it at least twice to pick it up, as the connection with other points is very weak.

"As an explanation for the Black Death in its own right, [bubonic plague spread by rat fleas] simply isn't good enough. It cannot spread fast enough from one household to the next to cause the huge number of cases that we saw during the Black Death epidemics," said Public Health England's Dr Tim Brooks.

I.e. Flees are not a fast enough vector. It must have been something faster.Enter airborne plague. And the 1906 case as an example of how fast it moves.And the presence of "DNA of Yersinia pestis" on the teeth of the corpses of the people from the period, as a proof that they COULD HAVE been spreading it with their breath. Too.

The find actually does not exclude fleas, it only (maybe) provides proof for YET

Onky SOME had the DNA. What about the others?From what I remeber goint to school. The rats hellped spreading the plague, because they had access to the homes and the cities. This ment that even closing the doors and even city gates did not stop the spreading.

It might have slowed it down a little bit, but rats (or rather the fleas on the rats) still had access to the humans.Then when it was inside a house or a city, contact between huimans helped spreading it further and faster.

I am sure if you look further, dogs might have had fleas as well and thus also spread it.

This is pretty spot on. The whole issue appears to be the tendency of some people to try and condense the truth into a general statement, such as, "fleas on rats spread the bubonic plague." Of course the truth is more complex and may not be fully understood, but I don't think serious scholars ever asserted that fleas on rats were the only mechanism by which the disease was spread. The important part of the theory was that fleas on rats on boats brought the bacteria from China to Europe and then facilitated

From the article (which is really a veiled advertisement for an upcoming tv show), researchers found the bacteria on the teeth of the skeletons and use this as proof that the plague spread by humans and not rats (the article actually calls it a virus, but that the black plague was bacterial, not viral).

It is reasonable that if people died from a bacterial infection y.pesis, that said bacteria would remain on their dead bodies and be burried with them. The fact that they found DNA of the bacteria on the teet

Having just done something very un-slashdot-like (well, it *used* to be what a lot of us did, but not the last few years), i noted that it was hitting in the midst of a famine... which is when a) many, many people would have weakened immune systems, and b) did you unbelievably rich folks, who can eat three meals a day (or more)(or supersized) without thinking about it think that the concept of stewed rat was only in, say, Monty Python?

And if the fleas hit the folks catching them, and then it mutated, or the

There is some argument missing here. The usual story is that rats infected humans by spreading fleas that spread the microbe through bite.. I am not sure what the finding says about humans. Was mankind a vector of the flea? That might not be all that surprising as fleas and ticks often cam be spread by other mammals to humans. The novelty is that the flea could live on people without the rat host being necessary.

Of course the plague was spread by humans. Otherwise you would have to conclude that rats walked all over continental Europe over the course of a few years.

While I'm pretty certain that humans were a main vector in spreading the plague, your "otherwise" doesn't hold water.It's enough that rats move enough to get in contact with other rats. And they do. They have overlapping and somewhat fluid territories, and young rats without a territory needs to go find one.

There are many historic examples of the black plague apparently spreading by ship. Nothing proven, but strong circumstantial evidence. City 1 has plague. Ship arrives from city1 at city2. Shortly thereafter the first case of plague happens in city2.

The pneumonic form of plague is faster. Even flea-mediated transmission between people would likely produce obviously sick or dead crew before a ship reached its destination.

The plague was so insidious because the bacteria could live in an animal reservoir (rats carried on ships) and ALSO spread quickly between people. The rats carried it long distances, such as on sea voyages, then infected people, who then infected other people.